The invention relates to a semiconductor device having an insulating substrate and comprising at least one Schottky diode which is formed between a metal layer situated on the substrate and a semiconductor layer of polycrystalline or amorphous silicon which lies partly on the metal layer and which extends partly outside the metal layer over a lateral surface of the metal layer. The invention also relates to a method of manufacturing such a device and to a display device and a support plate for this device comprising such a semiconductor device.
Such a semiconductor device is suitable inter alia for use in a display device for displaying alphanumerical and video information by means of passive electro-optical display media such as liquid crystals, electrophoretic suspensions, and electrochromic materials.
A semiconductor device of the kind mentioned in the opening paragraph is known from British Patent Application 2,129,183, in particular from FIG. 27 and the corresponding part of the description on pp. 6 and 7 of the said Patent Application. A semiconductor device is described therein which forms part of a matrix display device with switching elements comprising a Schottky diode which is formed between a metal layer situated on an insulating substrate and a semiconductor layer of polycrystalline or amorphous silicon which extends over the metal layer, overlapping the latter. The use of such a semiconductor device has many advantages, among them a simple manufacture and a low crosstalk. It is further noted in the British Patent Application that the lateral leakage current path, which occurs in a semiconductor device having a PIN diode overlapping the subjacent metal, is absent in a device having a Schottky diode, so that the leakage current in the reverse direction is lower.
A disadvantage of the known semiconductor device is that the Schottky diodes therein still turn out to have a high reverse current. In addition, as practice has shown, the reverse current strongly increases especially at reverse voltages across the diode of 2 to 10 Volts. As a result, the known semiconductor device is less suitable for use in a matrix display device since the reverse voltages usual in such devices, which are above 2 Volts, cause the charge with which the corresponding picture element is kept at the desired voltage to flow away prematurely.